J24 Memorandums, Hints, Precepts, a?td Recipes, ^e. 



make a good fitting of large pieces of iron work, which ren- 

 ders it neceflary fometinies to join and feparate the pieces 

 repeatedly before a proper adjaftment is obtained. AV'hea 

 this is expefted, the white lead ought to predominate in the 

 mixture, as it dries much flower than the red. A workman, 

 knowing this faft, can bti at little lofs in exercifing his own 

 difcretion in regulating the quantities. It is fafeft to err on 

 the iidc of the white lead, as the durability of the cement 

 is no way injured thereby, only a longer time is required lor 

 it to dry and harden. 



When the fittings will not admit eafily of fo thick a fub- 

 fiance as flannel being interpofed, linen may be fublUluted, 

 or even paper or thin palteboard ; the only reafon for em- 

 ploying any thing of the kind being the convenience of 

 handling. 



This cement anfwers well alfo for joining broken ftones 

 however large. Citterns built of iquare ftones, put together 

 •with this cement, will never leak or want any repairs. In 

 this cafe the ftones need not be entirely bedded in it, an inch 

 or even lefs of the edges that are to lie next the water need 

 only be fo treated : the reft of the joint may be filled with 

 good lime. 



XXIV. Another Cement that will jl and the Action of boilmg 

 IVater and Steam. 



This cement, which is preferable even to the former for 

 fleam-engines, is prepared as follows : 



Take % ounces of fal-ammoniac, i ounce of flowers of 

 fulphur, and 16 ounces of caft-iron filings or borings. Mix 

 all well together by rubbing them in a mortar, and keep the 

 powder dry. 



When the cement is wanted for ufe, take one part of the 

 above powder and twenty parts of clean iron borings or filings, 

 and blend them intimately by grinding them in a mortar. 

 Wet the compound with water, and, when brought to a con- 

 venient confiftence, apply it to the joints with a wooden or 

 blunt iron fpatula. 



Ey a play of affinities, which thofe who are at all acquainted 

 with chemiftry will be at no lofs to comprehend, a degree of 

 aftion and reaction takes place among the ingredients, and 

 between them and the iron furfaces, which at laft caufes the 

 whole to unite as one mafs. In faft, after a time, the 

 mixture and the furfaces of the flanches become a fpecies of 

 pyrites (holding a very large proportion of iron), all the parts 

 of which cohere llrongly together. 



XXV. All' 



